1. Field of the Invention
The present invention relates to an apparatus for forging a ring of a large caliber.
2. Background
A conventional apparatus for forging a ring of a large caliber is disclosed in Japanese Patent Publication No. 53-9182. In particular, the conventional forging apparatus includes a vertical cylinder device which generates a pressurized liquid when a vertical ram thereof is pressurized by a source of pressurization, and a horizontal cylinder device communicating with the vertical cylinder device and having a horizontal ram adapted to move forward when the pressurized liquid is supplied thereto from the vertical cylinder device. An anvil is mounted to the horizontal ram and to a return cylinder device connected to a supply source of hydraulic pressure and having a return ram to return the anvil to a return position. A mandrel is provided in opposing relationship to the anvil and is supported by upper and lower tension bars in such a manner that a peripheral portion of the ring blank can be received between the anvil and the mandrel for forging the ring blank. Finally, a table roller device is provided around the periphery of the ring blank for rotationally driving the ring blank.
In the above-mentioned structure, if the vertical cylinder device is pressurized by the pressure source, such as a hydraulic press or the like, then the hydraulic pressure is applied to the horizontal cylinder device communicating with the vertical cylinder device to thereby move the anvil forward, so that a portion of the ring blank is compressed and forged between the anvil and mandrel. After completing the forging of the predetermined portion of the ring blank, the pressurization of the vertical cylinder device is removed and the anvil is returned by the return cylinder device, thereby returning both the horizontal and vertical cylinder devices to their respective original positions. Thereafter, the table roller device is driven to thereby rotate the ring blank by a predetermined angle, so that another portion of the ring blank can be forged in the same manner as mentioned above. In this manner, the entire periphery of the ring of the caliber can be forged.
In a conventional forging press, a crosshead for mounting an anvil is adapted to slide parallel to and along a press column. On the other hand, in the above-mentioned conventional large caliber ring forging apparatus, due to the fact that a portion of the press column includes the upper and lower tension bars which can be freely opened and closed, it is not possible to provide a sliding part to thereby control undesirable movements. Also, due to the fact that the vertical and horizontal cylinder devices communicate with each other, unless the ring blank is properly arranged such that the center of the ring blank in the vertical direction exactly coincides with the center of the horizontal cylinder device in the vertical direction, a difference in reaction force between the upper and lower portions of the horizontal cylinder device will be generated to thereby incline the anvil, with the result that the ring blank may be forged in a tapered manner. In addition, even if the ring blank is properly arranged, a difference in reaction forces can be generated due to the difference in temperatures between the upper and lower portions of the ring blank to be forged (including a temperature difference created when heating and cooling the ring blank during the forging process), which causes the anvil to be inclined so that the ring blank may be formed in a tapered manner.
Also, after completion of forging of a predetermined portion of the ring blank, when the table roller device is driven to rotate the ring blank, the mandrel and the forged portion of the ring blank, which are shaped so as to fit each other, produce a frictional force between them, thereby making it difficult to rotate the ring blank a predetermined angle with accuracy by driving the table roller device along. Therefore, there arises situations where it is necessary to forge the same portion of the ring blank two or more times. As a result, there is produced a forged ring which has an inferior final shape. Moreover, after the forging of the predetermined portion of the ring blank is completed, when the pressure applied to the vertical cylinder device is removed, the anvil is returned by the return cylinder device and the horizontal and vertical cylinder devices are both returned to their original positions. During this procedure, there is a slight time lag between the removal of the pressurization of the vertical cylinder device and the subsequent pressurization of the return cylinder device, resulting in a loss of efficiency.